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WL-PM-E/Letter to: DRMS Subject: Response to Comments <br />• stability of the exposed rock, and where necessary, will be buttressed by <br />placement of additional rock or barriers, to ensure long-term stability. <br />Where exposed rock faces are stable at steeper slopes, up to vertical, and <br />where safety and appearance are acceptable (usually for slopes of less than 10 <br />feet in height), the exposed bare rock face may be left in place, particularly <br />near and in road cuts where they may be monitored closely during the period <br />between their construction and completion of mining on the property. <br />Where exposed rock may be stable but subject to erosion, sluffing, or rockfalls, <br />the overall slope will be backfilled with cobbles and other large materials (which <br />may include gabions) to 2H:1 V or flatter, where possible. Some smaller slope <br />sections (of up to six feet in height) of steeper grade (1:l or 1.5H:1 V) will remain. <br />Selected areas shall have soil placed in pockets and vegetated with grass, while <br />other selected areas will have trees and shrubs transplanted from areas being <br />stripped (as discussed on page 2, #5). These will be protected by barriers at the <br />toe of the slope ("turnpike barriers" or dry-laid concrete blocks to catch sluff ing <br />material and provide long term protection. <br />4. Unconsolidated cut slopes will be graded to 3H:1 V whenever possible, and <br />steeper slopes shall be limited to not more than six feet for 2H:1 V, and not more <br />than three feet for 1:1 slopes, unless the material is clearly stable (as determined <br />by an inspection and report by an engineer). As with backfilled areas (see item <br />2 above), these will be graded, have soil placed in selected area, and <br />vegetated with grass and browse vegetation per BLM "mitigation measures" and <br />approved seeding plan, in order to provide long-term stability. <br />b. As required by BLM (see page 2, #6), the top of all pit walls (whether sloped or not) <br />shall have berms constructed. The tops of all slopes of greater than 3H:1 V shall be <br />evaluated and as determined by engineer or BLM inspectors, shall be protected <br />against significant runon of water and erosion by placement of berms and construction <br />of permanent armored channels for water flow which cannot be diverted to other <br />locations. <br />c. These berms shall be tied in with swales or other drainage structures necessary to <br />protect against erosion of both disturbed and undisturbed areas. The need for such <br />structures shall be identified by on-site inspections with the BLM and operator's <br />engineer; the DRMS will be notified and invited to such inspections. The BLM bond is <br />designed to provide for the additional costs necessary to build and maintain such <br />structures, if necessary due to unexpected closure of the operation, and therefore may <br />not need to be included in the DRMS bond. <br />d. It is understood and confirmed that the above practices may need to be revised, <br />and may require filing of a technical revision, in the future, based on DRMS and BLM <br />evaluation. <br />e. The term "target slope" is intended to mean the overall slope of a given area, but to <br />• make it clear that some small portions of that area may have shallower or steeper <br />slopes due to placement of rills, placement of rocks/boulders, woody debris, and trees. <br />PROJECT: Montoya Pit M-1980-146 AM-4 15 July 2010, Page 5